The present invention generally relates to an oxabicyclo monomer and a photoresist polymer formed therefrom, a photoresist composition containing said polymer, and a method of forming a photoresist micro pattern using the polymer. During the manufacture of a micro circuit of a highly integrated semiconductor device, the polymer of the present invention can be used as a photoresist in a photoresist lithography process using a KrF(248 nm) or an ArF(193 nm) light source. These are the light sources usually applied in the manufacture of 1G and 4G Dynamic Random Access Memory (xe2x80x9cDRAMxe2x80x9d) semiconductor devices.
In general, an ArF photoresist usually requires excellent etching resistance and adhesiveness as well as low light absorbance at 193 nm wavelength. The ArF photoresist should also be developable by using a 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution. Up to now, many researchers have focused on photoresist resins having an etching resistance and transparency to 193 nm wavelength similar to that of novolac-type resins. This work is described, for example, in the following articles: xe2x80x9cSynthesis and Dissolution Characteristics of Novel Alicyclic Polymers With Monoacid Ester Structuresxe2x80x9d (Takashi Hattori et al., Journal of Photopolymer Science and Technology, 1997, Vol. 10, No. 4, pp. 535-544.), xe2x80x9cNew Protective Groups in Alicyclic Methacrylate Polymers for 193 nm Resistsxe2x80x9d (Ibid., pp. 545-550), and xe2x80x9cChemically Amplified Resist Based on High Etch-Resistant Polymers for 193 nm Lithographyxe2x80x9d (Ibid., pp. 561-570) and so on. To obtain an etching resistance similar to that of a novolac-type resin, an ArF photoresist resin should contain an alicyclic group. However, alicyclic-type resins generally have poor adhesiveness. A micro pattern using an alicyclic-type resin is illustrated in FIG. 1. The alicyclic-type resin used to form the pattern in FIG. 1 has good resolution, but poor adhesiveness. Thus, a pattern collapse occurs such as that shown in FIG. 1. As a result, it is very difficult to practically apply such a resist to a semiconductor device.
The photosensitive properties of the photoresist resin are affected by the monomer type used to form the photoresist resin. Thus, photosensitivity, etching resistance, adhesiveness, resolution, and so on varies depending on the monomer type introduced into the photoresist resin. In addition, the monomers conventionally used to form the photoresist resin are expensive, thus making it difficult to mass-produce the photoresist resin using conventional monomers. Therefore, the invention of a monomer which would allow the mass-production of a photoresist resin having excellent photosensitive properties, is advantageous.
In accordance with the present invention, it has been found that when a heterobicyclic compound, which contains an alicyclic group, is used as a monomer to form an ArF or a KrF photoresist resin polymer, the etching resistance is excellent, the pattern collapse of FIG. 1 can be prevented because of the excellent adhesiveness of the photoresist, and the photoresist resin can be mass-produced economically because the monomer is inexpensive.
Heterobicyclic compounds of the present invention are represented by the following formula: 
where
Z is O or S;
X is a moiety of the formula: 
each of R1 and R2 is independently hydrogen or a C1-C4 substituted or unsubstituted straight or branched chain alkyl group; and
m is an integer from 1 to 4.
The present invention also relates to a method of preparing the above described heterobicyclic compound.
Preferably, X is 2-hydroxy ethyl, 2-hydroxy propyl, 3-hydroxy propyl, 2-hydroxy butyl, 3-hydroxy butyl, 4-hydroxy butyl, or 2-methyl-3-hydroxy propyl
In another embodiment, the present invention provides a polymer derived from a monomer comprising the compound of formula 1. The monomer can further comprise one or more of the compounds selected from the group consisting of t-butyl 5-norbornene-2-carboxylate and compounds of the formula: 
where Y is hydrogen or a carboxylic acid group. In addition, the monomer can include maleic anhydride. Furthermore, the monomer can include tert-butyl 5-norbornene-2-carboxylate.
Polymers of the present invention which is derived from a monomer comprising the heterobicyclic compound of the above Formula 1 include polymers of the formula: 
where X and Z are those defined above; Y is a hydrogen or a carboxylic acid group; and a, b, c, and d are relative ratio of each monomeric units. It should be appreciated that the order of each monomeric units represented in a polymer formula of the present invention does not necessarily indicate the actual order of such monomeric units in the actual polymer. The monomeric units represented in the polymer formula is simply intended to indicate the presence of such monomeric unit in the polymer, i.e., when the variable a, b, c, or d is not 0. Moreover, the variables a, b, c, and d represent the total relative ratio of each units. For example, the total amount xe2x80x9cdxe2x80x9d of polymeric units derived from maleic anhydride may be inter dispersed throughout the polymer (not necessarily in same concentrations) or all or majority of such polymeric unit may be concentrated in one particular location of the polymer. Preferably, the ratio of a:b:c:d is (5-90%):(10-90%): (0-50%):(50-120%). The present invention also relates to a method of preparing the above polymer.
Furthermore, the present invention relates to a photoresist composition comprising a polymer of Formula 2, a photo acid generator, and an organic solvent.
The present invention also relates to a semiconductor device manufactured by using the above photoresist solution, and a method of forming an ArF or a KrF photoresist pattern in the manufacture of such a semiconductor device.